1. Technical Field
The present invention relates to a shielding structure of a shielding electric wire which is formed by ultrasonic welding a shielding electric wire and a ground wire with the use of two resin members.
2. Related Art
A conventional shielding structure using ultrasonic welding has been disclosed in Unexamined Japanese Patent Publication 2001-6767. The shielding structure is formed by using two resin members 50 and 51 having arcuate channels 50b and 51b formed on mutual junction faces 50a and 51a and an ultrasonic horn as shown in FIGS. 13(a) and 13(b). More specifically, as shown in FIGS. 14 to 17, a ground wire 53 is mounted in the upper position of a shielding electric wire 52 having the outer periphery of a core 52a covered with a braided wire (a shielding member) 52c and the shielding electric wire 52 portion mounting the ground wire 53 is interposed between the two resin members 50 and 51 to apply an ultrasonic vibration by means of the ultrasonic horn while compressing the two upper and lower resin members 50 and 51.
When the ultrasonic vibration is applied by the ultrasonic horn, the resin members 50 and 51, an insulating outer cover 52d of the shielding electric wire 52 and an insulating outer cover 53b of the ground wire 53 are fused by a vibration energy in the application of an ultrasonic wave so that a core 53a of the ground wire 53 and the braided wire 52c of the shielding electric wire 52 are brought into a contact state. When the application of the ultrasonic wave is completed and the fused portions are solidified, the two resin members 50 and 51 are integrated so that the shielding electric wire 52 and the ground wire 53 are fitted to each other.
In the conventional shielding structure of the shielding electric wire 52, however, the junction faces 50a and 51a of the two resin members 50 and 51 are simply butted against each other. For this reason, there is a possibility that a shift might be caused between the two resin members 50 and 51 due to the ultrasonic vibration.
In order to solve the foregoing, it can be proposed that protruded portions are provided on the junction faces 50a and 51a of the two resin members 50 and 51 and holes are provided on the other junction faces 50a and 51a respectively to position the two resin members 50 and 51. In addition, it can be suggested that the bottom face side of the hole is set to be an inclined face and a vibration energy is caused to converge in such a manner that the tip face of the protruded portion is caused to come in line contact with the inclined face. By such a structure, the tip side of the protruded portion and the portion abutting thereon are promoted to be fused so that a sticking force between the two resin members 50 and 51 can be enhanced.
In the case in which a reaction force received from the inclined face by the tip face of the protruded portion is unbalanced in a transverse direction, however, there is generated a situation in which the protruded portion is broken due to the vibration in the application of the ultrasonic wave and the sticking force between the two resin members 50 and 51 is thus reduced. If the contact area (the line contact distance) of the tip face of the protruded portion and the inclined face in the hole is too small, moreover, a portion on which a vibration energy directly acts is reduced so that the sticking force between the two resin members 50 and 51 cannot be enhanced effectively.
Further, as shown in FIG. 17, however, in a state in which the shielding electric wire 52 and the ground wire 53 are interposed between the two resin members 50 and 51 in the execution of ultrasonic welding, only the arcuate channels 50b and 51b of the resin members 50 and 51 are fitted to the shielding electric wire 52 and the ground wire 53 and electric wire peripheral faces 50c and 51c provided on peripheral edges thereof are separated from each other. Accordingly, a vibration energy in the application of an ultrasonic wave converges on only the shielding electric wire 52 and the ground wire 53 until the ultrasonic welding progresses so that the electric wire peripheral faces 50c and 51c are fitted to each other. When the vibration energy excessively converges, thus, an insulating inner cover 52b of the shielding electric wire 52 is also fused and an interval between the core 52a and the braided wire 52c is not sufficiently maintained so that the insulating performance of the shielding electric wire 52 is deteriorated. In the worst case, there is a possibility that the core 52a and the braided wire 52c might be short-circuited.
In the conventional shielding structure of the shielding electric wire 52, moreover, the junction faces 50a and 51a of the two resin members 50 and 51 are simply butted against each other. For this reason, there is a possibility that a shift might be caused between the two resin members 50 and 51 due to the ultrasonic vibration.
In order to solve the foregoing, it can be proposed that protruded portions are provided on the junction faces 50a and 51a of the two resin members 50 and 51 and holes are provided on the other junction faces 50a and 51a respectively to position the two resin members 50 and 51. By such a structure, the two resin members 50 and 51 can be prevented from being shifted from each other, and furthermore, the tip of the protruded portion and the bottom face portion of the hole are fused so that a sticking force between the two resin members 50 and 51 can be enhanced.
When the electric wire abutment faces of the arcuate channels 50b and 51b of the resin members 50 and 51 are not fitted to the shielding electric wire 52 and the ground wire 53 but only the protruded portion is set to be fitted to the bottom face of the hole in the state in which the shielding electric wire 52 and the ground wire 53 are interposed between the two resin members 50 and 51, however, the vibration energy in the application of the ultrasonic wave converges on only the protruded portion, resulting in the generation of a situation in which the protruded portion is broken. Consequently, the sticking force between the two resin members 50 and 51 is reduced. As a result, an electric wire holding force is decreased.